CLN3 Batten disease is a fatal lysosomal storage disorder (LSD) resulting from autosomal recessive mutations in CLN3. The disease progresses from vision loss in early childhood to seizures, motor decline, cognitive disability and dementia, with a typical life expectancy of 15-30 years of age. There is no cure for CLN3 Batten and the only treatments available address some disease symptoms, but do not delay disease progression. The discovery of an effective treatment for CLN3 Batten has been hindered by a lack of understanding of the protein's function and the underlying mechanisms leading to neurodegeneration. The goal of this proposal is to test a therapeutic approach for CLN3 Batten that employs antisense oligonucleotides (ASOs) and in so doing, elucidate mechanisms of neurodegeneration in this disease that will inform research and discovery of effective treatments for Batten diseases and other LSDs. Most cases of CLN3 Batten are caused by deletion of exons 7 and 8 (CLN3?78), which results in an open reading frame shift and a premature termination codon. We hypothesize that using ASOs to redirect pre-mRNA splicing and correct the reading frame of CLN3?78 mRNA will partially restore protein function and have a therapeutic effect in CLN3 Batten disease. Our preliminary findings support our hypothesis, demonstrating that restoring the CLN3?78 reading frame alleviates dysfunction associated with disease in both cell and animal models. We will test our hypothesis in the proposed project with the aims to 1) compare the function of the wild type and novel CLN3 isoforms, 2) develop an approach using ASOs to increase CLN3?ex78 isoforms, 3) assess ASO treatments for CLN3 Batten disease using human cell lines as well as mouse and 4) porcine models of CLN3 Batten disease. Collectively, this study will allow us to better understand the function of the CLN3 protein and the utility of ASOs in treating CLN3 Batten disease.